Laparoscopy has been widely used in surgeries for the gastrointestinal tract, the abdominal wall, the endocrine system, etc. Different from the traditional laparotomy where the surgeon performs surgery in the abdominal cavity through a single large incision, laparoscopy only requires small incisions (usually 0.5 cm-1.5 cm) for insertion of a variety of cannulas, such that medical devices and the laparoscope lens can enter the abdominal cavity through the cannulas for the surgeon to perform operation while watching images captured by the laparoscope. Laparoscopy enables the surgeons to achieve the same effect as the traditional laparotomy with smaller wounds.
However, if the temperature of the laparoscope lens is lower than the temperature inside the abdominal cavity, the warm air in the abdominal cavity may result in fogs on the laparoscope lens, thereby hazing the laparoscopic images displayed on a screen, and adversely affecting the operation. Dehazing techniques were developed to solve this issue. However, the dehazed images usually have problems of color cast.
In a conventional method to correct color cast of the dehazed image, representation of the dehazed image is converted into an HSV (hue, saturation, value) color space, so as to correct the dehazed image by promoting the value component (i.e., lightness) of the image.
Nevertheless, in laparoscopy, light is provided only by the laparoscope, so environmental brightness may be unstable due to movement of the laparoscope, other devices or tissues in the abdominal cavity. The lightness of the laparoscopic images may be affected by the environmental brightness, thereby causing further color cast in the corrected dehazed image, which is the resultant image obtained after correcting the dehazed image using the conventional method. As a result, the conventional method is not suitable for applications with great environmental brightness variation, such as laparoscopy.